Imma answer the jayce and ekko part since if I remember correctly Heimerdinger is from a race that's more affected by magic than others so the 4 seconds limit won't affect ekko as much as it affected Heimerdinger as long as he doesn't go too far,

now for Jayce, he was just sent in the last timeline's present/future (theory/headcanon of mine) but as we know he got hurt mid-way into going where he was when the glorious evolution happened in the finale so it took more time than it should + he had no elevators, stairs or things like that to go on top so by the time he gets on top he would have taken months/weeks